Fire Alarm System for Considerable Areas.

Where the area is more extensive and the number of stations considerable, the system illustrated in [Fig. 70] is very suitable. It consists of the requisite number of break-glass boxes, bells and a more elaborate annunciator system. In general details it resembles the last system, but uses a relay to send out the current for ringing the alarm bells.

When a box operates, the current impulses sent on the line act on the relay instead of directly on the bells. Each stroke of the relay closes a local circuit which includes the bells and the battery.

This system does away with large batteries and is very economical of wire. The current needed for the relay is very small, whereas in a direct system of any size, the current and voltage to ring a number of bells located at wide intervals would be prohibitive.

The reference letters are as follows: AA are the alarm bells, BB the break-glass alarm boxes, C is the annunciator bell, D is the relay which remains closed when an alarm comes in keeping the bells constantly ringing until shut off. E is a resistance coil and F is the battery.

A system cut-out switch G and JJ switches on the annunciator for controlling individual circuits are also provided. HH are the annunciator drops and K is a constant-ring switch which can also be used for a general alarm to ring all the bells at once.

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1.The Study of Electricity for Beginners.
2.Dry Batteries, How to Make them.
*3.Electrical Circuits and Diagrams, Part 1.
4.Electric Bells, Annunciators and Alarms.
5.Modern Primary Batteries.
6.Experimenting with Induction Coils.
*7.Electric Gas Igniting Apparatus.
*8.Small Accumulators, How to Make and Use.
9.Model Steam Engine Design.
*10.Practical Electrics.
11.Inventions, How to Protect and Sell them.
12.Woodwork Joints, How to Make and Use.
*13.The Fireman’s Guide to the Care of Boilers.
*14.The Slide Valve Simply Explained.
*15.The Magneto Telephone.
*16.The Corliss Engine and Its Management.
*17.Making Wireless Outfits.
18.Wireless Telephone Construction.
*19.The Wimshurst Machine, How to Make It.
20.Simple Experiments in Static Electricity.
21.Small Electrical Measuring Instruments.
22.Electrical Circuits and Diagrams, Part 2.
*23.Induction Coils, How to Make Them.
24.Model Vaudeville Theatres.
*25.Alternating Currents, Simply Explained.
*26.How to Build a 20 foot Bi-plane Glider.
*27.A B C of the Steam Engine.
*28.Simple Soldering, Hard and Soft.
*29.Telegraphy for Beginners.
30.Low Voltage Lighting with Storage Batteries.
33.House Wiring for Electric Light.
34.Magnets and Magnetism.
*36.Small Windmills and How to Make Them.
Injectors, Their Construction and Use. Keppy.
Refrigeration and Ice Making. Wakeman.
37.Collin’s Wireless Plans, Part 1.
38.Collin’s Wireless Plans, Part 2.